Integrated Electrochemical Conversion of Plastic Waste and CO₂ to Formate Using Non-Noble-Metal Catalysts: <i>In Situ</i> Raman Study

Poly(ethylene terephthalate) (PET), a common single-use plastic, significantly contributes to CO₂ emissions when discarded or incinerated. In this study, we have employed an innovative approach by combining electrochemical PET hydrolysate oxidation and CO₂ reduction reaction (CO₂RR) to simultaneously produce formate in a single electrochemical cell. Utilizing simple electrochemical methods, a porous 3D carbon felt (CF) electrode was anodically oxidized to produce activated carbon felt (aCF). The latter was used as a support for the electrochemical deposition of bismuth oxide carbonate (Bi₂O₂CO₃) and nickel cobalt phosphate (NiCoPO_<i>x</i>) for CO₂RR and anodic PET hydrolysate oxidation, respectively. <i>In situ</i> Raman analysis indicated that MOOH (M = Ni, Co) intermediates acted as active sites for PET hydrolysate oxidation, with the ability to regenerate into lower-valence nickel species post-reaction. Both electrodes exhibited Faradaic efficiencies (FEs) exceeding 90% in their respective half-cell reactions. When implemented in a two-electrolyzer setup, a combined FE of up to 158% for both reactions was recorded at a remarkably low cell voltage of 1.8 V. This research highlights the use of non-noble metals to transform PET plastic waste and CO₂ into valuable fuels.